May 25, 1955

1955In the United States, a night-time F5 tornado strikes the small city of Udall, Kansas as part of a larger outbreak across the Great Plains, killing 80 and injuring 273. It is the deadliest tornado to ever occur in the state and the 23rd deadliest in the U.S.^[†]

The Fujita scale, or Fujita–Pearson scale, is a scale for rating tornado intensity, based primarily on the damage tornadoes inflict on human-built structures and vegetation. The official Fujita scale category is determined by meteorologists and engineers after a ground or aerial damage survey, or both; and depending on the circumstances, ground-swirl patterns, weather radar data, witness testimonies, media reports and damage imagery, as well as photogrammetry or videogrammetry if motion picture recording is available. The Fujita scale was replaced with the Enhanced Fujita scale (EF-Scale) in the United States in February 2007. In April 2013, Canada adopted the EF-Scale over the Fujita scale along with 31 "Specific Damage Indicators" used by Environment Canada (EC) in their ratings.

1955First ascent of Mount Kangchenjunga: On the British Kangchenjunga expedition led by Charles Evans, Joe Brown and George Band reach the summit of the third-highest mountain in the world (8,586 meters); Norman Hardie and Tony Streather join them the following day.^[†]

Kangchenjunga is the third-highest mountain in the world. Its summit lies at 8,586 m (28,169 ft) in a section of the Himalayas, the Kangchenjunga Himal, which is bounded in the west by the Tamur River, in the north by the Lhonak River and Jongsang La, and in the east by the Teesta River. It lies in the border region between Koshi Province of Nepal and Sikkim state of India, with the West and Kangbachen peaks located in Nepal's Taplejung District and the Main, Central and South peaks directly on the border.